This invention relates to load handling pallets and load strapping means.
It is known to provide a reel unit for incorporation in a load handling pallet, e.g., a 4-way pallet, comprising a housing, a shaft rotatably mounted within the housing, a drum mounted on and rotatable with the shaft, a strapping strand, e.g., a strap, wound on the drum, an opening in the housing through which the strapping strand emerges, attachment means on the free end of the strapping. strand for securing the strand toa load on a pallet or for securing to anchorage means on a pallet after passing the strand over a load on the pallet, a rewind spring coiled round the shaft alongside the drum, stop means preventing the attachment means being drawn through the opening into the housing by the action of the rewind spring, a ratchet concentric with the drum and rotatable with the drum and shaft, with a pawl for engaging teeth on the ratchet to stop or prevent pulling of the strapping strand from the drum, means for effecting engagement of the pawl with the ratchet, and manually operable means is provided for tensioning the strapping strand when the pawl has been engaged with a tooth on the ratchet.
A pallet is described in EP-A-0 585 832 with reel units secured alongside spacer blocks below one side of the load receiving platform of the pallet, the strapping strands are straps, and the attachment means are loops for engagement with ski-tensioner type anchorage means in housings secured alongside spacer blocks below the opposite side of the platform. Alternatively, tensioning devices could be incorporated in the straps, or in the reel units, one form of the latter having a second ratchet concentric with the drum and rotatable with the drum and shaft, with a second pawl for engaging the teeth of the second ratchet to prevent rewind of the strap, a manually-operable change-over means being provided for selectively rendering one or other of the pawls inoperative, and tension being applied to the belt by a lever operated drive pinion engaged with a driven gearwheel secured on the shaft.
Another pallet is described in JP-A-10167267 with reel units secured one in a corresponding outer side of each of four corner spacers moulded integrally with a load receiving platform, the strapping strands are straps, and the attachment means are loops while the anchorage means are hooks within the outer sides of the corner spacers not occupied by the reel housings, which housings also carry lever mechanisms for tensioning the straps when the pawls are engaged with the ratchets.
Although the reel units in EP-A-0 585 832 can be readily added to existing 4-way pallets, many of which are made of wood, they are prone to damage because of being. located where contact can take place with forks of the fork-lift trucks. On the other hand, while the reel units in JP-A-10167267 are protected somewhat from the forks of fork-lift trucks by being incorporated in the corner spacers, such pallets are expensive and so are not likely to replace the millions of existing 4-way pallets.
One object of the present invention is, therefore, the provision of load strapping means for use wit existing 4-way pallets, particularlyxe2x80x94but not exclusivelyxe2x80x94those made of wood.
According to the present invention, load strapping means for use with 4-way pallets comprises a cap for placing on a load on a 4-way pallet, at least two strapping strands retractable through openings into housings at opposite sides of the cap, spring means for retracting the strapping strands, hooks on the free ends of the strapping strands for engagement with the underside of the platform of a 4-way pallet, tensioning means for tightening the strapping strands between the cap and the pallet after interposing a load between the cap and the pallet, and stop means for limiting retraction of the hooks into the housings when not engaged with a pallet.
Preferably, four strapping strands are provided, retractable into housings one on each side of the cap; and the positions of the housings in the cap preferably causes disposition of their openings to correspond to the middle spacers of a pallet. Alternatively, the cap may be in the form of a xe2x80x98spiderxe2x80x99 constituted by four housings conjoined in a cruciform, and the housings may be hinged together at the ends remote from their openings, to enable the spider to be collapsed into a compact bundle for delivery or return to a distributor.
However, because many loads to be palletized require overall caps to distribute strapping and/or stacking loads, e.g., products such as foodstuffs in cardboard boxes and/or cartons, or caps with depending flanges to embrace loads made up of a plurality of boxes and/or cartons, it may be convenient to provide the housings within the thickness of the cap.
Each strapping strand may be a wire or nonmetallic rope retractably wound spirally on a xe2x80x98thinxe2x80x99 reel within the respective housing and having a short cylindrical core between annular flanges spaced apart by negligibly more than the overall diameter of the rope, so that the rope will be wound spirally on the core, the axis of the reel being perpendicular to the general plane of the cap, the core being on a shaft rotatably mounted within the housing, there also being provided a rewind spring coiled round the shaft alongside the reel, stop means limiting the extent to which the hook can be drawn into the housing by the action of the rewind spring, a ratchet concentric with the reel and rotatable with the reel and shaft, with a pawl for engaging teeth on the ratchet to stop or prevent pulling of the rope from the reel, and manually-operable means for tensioning the rope when the pawl has been engaged with a tooth on the ratchet, particularly characterized in that each tooth of the ratchet has a pawl-engageable face inclined forwardly from its radially inner end with respect to a radial line from the axis of be shaft through said radially inner end of said face and with respect to the direction of unwinding of the rope from the reel, the pawl has a complementary face for mutual engagement with said face of any one tooth of the ratchet, the pawl is provided with spring-loading means with manually-operable means for changing the effect of the spring-loading over between urging the pawl into engagement with the ratchet and towards a position holding the pawl clear of the ratchet, and in that the manually-operable tensioning means is by way of a separate wrench engageable with one end of the shaft. The angle of inclination of said face of each tooth of the ratchet is preferably at least 10xc2x0 to said radial line from the axis of the shaft.
Having installed this reel unit in a cap to bear on a load on a pallet with the manually-operable changeover means for the spring-loading means of the pawl set to hold the pawl clear of the ratchet, the rope can be unwound from the reel, as by pulling the hook, to whatever extent is required or to enable the rope to be secured to the pallet by the hook, then the manually-operable change-over means is set for the spring-loading means to urge the pawl into engagement with the ratchet, whereupon the manually-operable tensioning means can be operated to tension the rope. Because of the mating complementary inclined faces of the pawl and any one of the teeth of the ratchet that it engages, the manually-operable change-over means can be set to the position in which the spring-loading means urges the pawl towards the position clear of the ratchet but without withdrawing the pawl from the ratchet until, when it is desired to release the load from the pallet, slight additional tensioning of the rope. effected as by means of a separate wrench applied to the shaft, the consequent slight rotation of the ratchet causes the mating complementary faces of the pawl and the engaged tooth to be separated enough for the spring-loading means to withdraw the pawl clear of the ratchet, whereafter the hook can be released from the pallet, so that the rewind spring is free to act on the shaft to enable the rope to be rewound on to the reel.
The spring-loading means is preferably a flexible tongue formed integrally with the pawl, and the manually-operable change-over means comprises a knob on the free end of the tongue of the pawl manually movable from one side of a projection on the housing to the other side of the projection, and the projection is preferably also resilient.
Because of the xe2x80x98thinnessxe2x80x99 of such a reel, a pair of reels may be incorporated on a single shaft within a housing, with a single rewind spring, ratchet and pawl, the two openings from the housing for the two ropes being provided at sides of the cap adjacent to each other, a similar double-reel unit being provided for ropes to openings at the other two adjacent sides of the cap.
Alternatively, each strapping strand may be a strap, there being within the respective housing parallel guides between ends of the housing, at one end of which is the opening, a crosshead slidable along the guides towards and away from the opening, the crosshead being mainly constituted by crossbars of graduated diameters; a fixed array of graduated crossbars adjacent the opposite end of the housing from the crosshead, the axes of the crossbars in the crosshead and the fixed array all being in a common plane with the smallest diameter crossbars being the nearest to each other, the strap having its inner end secured to one of the smallest diameter crossbars and being lapped in multi-purchase array round the other smallest diameter crossbar and each successively greater diameter crossbar in the crosshead and fixed array in turn, and with the final lap of the strap emerging from the opening in the housing, and spring means to urge the crosshead away from the fixed array; the total length of strap that can be accommodated being principally dependent on the number and lengths of laps between the crosshead and the fixed array, and the number of laps being determined by the number of crossbars in the crosshead and in the fixed array (e.g. three crossbars in one and two in the other giving five laps), the diameters of the crossbars can be but a few millimetres each consistent with being strong enough to carry the loads in the strap generated by the spring means.
The crossbars, in both the crosshead and in the fixed array, other than that smallest one to which the strap is secured, may be rollers rotatable with respect to side cheeks of the crosshead slidable along the guides or side cheeks secured to or integral with one end of the housing; or some or all of them may be non-rotatable and provided with low friction surfaces.
The guides may be channels along which slide wings on the crosshead and accommodating coil compression springs. Alternatively the guides may be bars passing through the crosshead and encircled by coil compression springs. Alternatively, the spring means may be a tension spring or springs.
The tensioning means may be a lever mechanism with an over-centre locking action, or with a rotational device within the housing adjacent the opening with a push-lock action or spring catch.
The stop means for preventing the hook being drawn through the opening into the housing may be afforded by making the hook wider than the opening, and the latter may be recessed within the housing end so that the hook will not project significantly therefrom when the strap is fully retracted. Alternatively a recess may be provided in the underside of the cap or lid for engagement by the hook
Each hook preferably has two prongs spaced apart by at least the width of a middle spacer of a pallet, so that the prongs can engage the underside of the platform one to each side of the spacer, without being in danger of damage or dislodgement by the forks of a fork-lift truck. Conveniently, when not engaged with a pallet the hooks engage the housings around the opening, the housings thus constituting the stop means; and the openings are preferably recessed with respect to the sides of the cap, so that when not engaged with a pallet the hooks are shrouded within the sides of the cap where they cannot cause injury to personnel.
The cap may be nestable within similar caps and/or with a pallet, for convenience when returning caps and pallets to a distributor.
A transponder may be incorporated in the cap, to enable the cap and/or load secured thereby on a pallet to be tracked or traced.